It's not all that unusual that I need to edit a post already published that goes far back - and that creates a problem:

In order to find that post I have to load a list of sometimes several hundred post. It takes quite some time, and works some time - and sometimes not. In the latter case, I get "Error reading posts from server - XML parsing error: Overflow". I have a self-hosted Wordpress blog, version 2.7.1

It would be tremendously helpful if the "Edit posts already published" included some way of finding an old post: perhaps by date, or by title.
Thanks a lot!

There is nothing I can do - the interface between BlogDesk and WordPress only allows to read the last x posts from the beginning. And at some point, that's too much. If you want to edit very old posts, you need to login to WordPress.